Electron discharge tube circuit



Dec. 15, 194 M. J. O.'STRUTT ETAL 2,305,395

ELECTRON DISCHARGE TUBE CIRCUIT I Filed March 29, 1941 Fi .1 I geaormhr fLeqZborL INVENTORS MJO. 877F077 and A. MAN 05/? Z/El BY W ATIZORNEY Patented Dec. .15, 1942 UNITED STATES PATENT OFFICE ELECTRON mscnlmcn rum: cracmr Maximiliaan Julius om Strutt and Alder-t vander Ziel, Eindhoven, Net

herlands; vested in the .Alien Property Custodian Application March 29, 1941, Serial No. 385,792 In the Netherlands May 30, 1940 7 Claims. (cl.- 179-171) This invention'relates to a circuit-arrangement for amplifying, generating and/or frequency- ,transformation of electrical oscillations, which comprises a secondary electron-emission tube. In the present case a secondary-emission'tube is to be understood to mean a discharge tube whose electrode-system includes a cathode, a

control-grid, an anode and in addition at least- ,one electrode which is coated with a material having the property of readily emitting secondary [electrons when it'is struck by a stream of primary electrons.

For a proper understanding of the invention, reference will be had to the accompanying drawing in which Fig. 1 shows a circuit known in the art and upon which the present invention is an improvement, Fig. 2 is a known circuit, the principle of which is utilized in the invention, and Figs. 3 and 4 ,arecircuits of two embodiments .according to the present invention.

It is known that in a circuit-arrangement comprising a secondary-emission tube regenerative back-coupling can be obtained in a simple -manner by connecting the secondary-emission electrode to the control-grid and to the cathode through suitable impedances. A diagram embodying this known circuit-arrangement is represented in Fig. 1 which shows a secondary-emission tube I comprising a cathode 2, a controlgrid 3, a screen-grid 4, a secondary-emission electrode 5 and an anode t. Between the control-grid 3 and the cathode 2 is provided an input impedance 1 which may be constituted, for instance, by an oscillatory circuit tuned to the frequency of the oscillations to be amplified. Between the anode! and the cathode 2 is provided an output impedance I, the screenwgrid l is connected in the usual way to the cathode through a condenser .I' having a high capacity. For the sake of simplicity .the direct current connections have been omitted in the drawing, but it will be appreciated that the control-grid 3 must he negatively-massed, whereas the electrodes 4, I and 8 must be positively biassed, the positive bias of the anode 8 being larger than that of the secondary-emissionelectrode I. 4 h

To obtain regenerative back-coupling an impedance Z1 is provided between the secondaryalternating current of the secondary-emission electrode is in phase with the alternating control-grid voltage; consequently the impedances Z1 and Z: are so chosen that ap art of this current flows to a control-grid without phase-displacement. In an amplifying circuit with regenerative back-coupling for undamping the circuit 1 or, at ultra-high frequencies, for removing the inputedamping of tube I, the impedance Z1 may, forinstance, be anohmic resistance, and the impedance-Z2 may be a coupling condenser whose impedance is small relatively to that of the circuit L In a mixing arrangement, in which the regenerative back-coupling serves for generating the local oscillations the impedance Z1 may, for instance, be constituted by an oscillatory circult tuned to the frequency of the local oscillatidns, whereas the impedance Z2 is constituted by a re'actance whose sign corresponds to that of the reactance constituted by the input-circuit I- of the local oscillations. In this case the circuit electrode is supplied to' the control-grid witha mission electrode and the cathode, while an impedance Zr-1s connected between the secondelectrode and the control-grid. 7 These impedances are so chosen that the input impedance I is supplied with-a current which is in phase with the alternating control-grid voltage. In this'case the fact is utilised that the ity, whereas aphase displacement of. must be lead of 90. The two said measures may be combined by giving the current, which flows throughthe impedance Z: to the control-grid, such a value and phase that both undamping and removal of the input-capacity is obtained. In this "way the input-impedance of the tube can be completely compensated at ultra-high frequencies.

It is to be noted that in the transmission of oscillations having a very high frequency, with which the transit time of the electrons .is'at least of the same order as the period of the oscillation tov be transmitted, the fact must be taken into account, that the 'altemating current of the secondary-emission electrode is displaced in phase relatively to the alternating control-grid voltage. When, for instance, this phase displacement amounts to about 90 a part of the current of the secondary-emission electrode must be transmitted without phase-displacement to the control-grid'for removal of the input-capacproduced-for removing the input-damping. For

disposing of the input-capacity the impedances Z1 and Z2, for instance, might then be both capacities or both ohmic resistances, and ior disposing of the input-damping Z1 might be an ohmic resistance and Z: a small capacity.

Furthermore it is known that in secondaryemission tubes it is advantageous to utilise the fact that the anode-current substantially corresponds and is oppositely directed to the current of the secondary-emission electrode, by connecting the output-impedance between the anode and the secondary-emission electrode, and by connecting the electric center of these imped-. ances to the cathode. In this way an output voltage can be obtained which is symmetrical with respect to earth as a result of which transition of a single stage to a push-pull stage can be obtained in a simple mar ner. A known circuit arrangement of this kind is represented in Fig. 2 in which the direct-current connections have been omitted again. In this case the output impedance 8 is connected between the anode 6 and the secondary-emission electrode 5, the

electric center III of circuit 8 being connected to the cathode. Through the circuit 8 is set up a symmetrical voltage relatively to earth, which voltage may be supplied to the input circuit of a push-pull stage.

The circuit-arrangement shown in the drawback that back-coupling oi the secondary-emission electrode to the control-grid for undamping the input-circuit and/or for removing the input-capacity, such as is used in the circuit shown in Fig. 1, is not possible because the provision of the required impedances Z1 and Z2 would entirely break the symmetry of the circuit.

According to the invention this drawback is ondary-emission electrode as a result of which the advantage is obtained that the circuit may be very simple, since the current of the first secondary-emission electrode will be substantially in phase with the alternating control-grid voltage.

The invention will be more fully explained by reference to Figures 3 and 4 of the accompanying drawing representing, by way of example, two embodiments thereof.

Fig. 3 shows a circuit including a tube which comprises two succeeding secondary-emission electrodes 5 and H. The first secondary-emission electrode 5, whose current is in phase with the alternating control-grid voltage at least at not too high frequencies, is connected across an impedance Z1 to the cathode and across an im- Fig. 2 has pedance Z: to the control grid, said impedances being so chosen as to obtain undamping of the input-circuit and/or a decrease in input-capacity of the tube. The secondary-emission electrode II which directly precedes the anode and whose current at least approximately corresponds and is oppositely directed to the anode-current is connected to the anode through the output-impedance 8, whereas the center I O of the outputimpedance is earthed.

Fig. 4 represents a circuit according to the invention, wherein the input-circuit is also connected in push-pull gement. The inputimpedance 1 is connected in push-pull arrangement to the control-grids 3 and 3' of two similar secondary-emission .tubes l and i', the centerli of the input-impedance I being connected to earth. Each of the tubes I and I comprises two succeeding secondary-emissionelectrodes 5, H and 5', II respectively. Oi each tube the first secondary-emission electrode 5 and 5' respectively is connected to the cathode and to the control-grid through suitable impedances Z1, Z2 and Z1, Z2 respectively. The centrally earthed output-impedance H is connected between the two anodes 6 and 6', the last secondary-emission electrode ll of the tube I being connected to the anode 6' of tube I through a condenser l3, and the last secondary-emission electrode ll of tube l"being connected to the anode 6 of tube 1 through a condenser ll.

What we claim is: v

1. A circuit-arrangement comprisinga second ary electron-emission tube, in which the tube used comprises a cathode, a control grid, at least two secondary-emission electrodes and an anode arranged in the order named, an input circuit connected between cathode and control grid, an output-impedance whose electric center is connected to the cathode connected between the anode and one of the secondary-emission electrodes, a first impedance connected from the other secondary-emission electrode to the control grid, and a second impedance connected from said electrode to the cathode, said impedances being of such value that a back-coupling current is derived from said other secondaryemission electrode and supplied to the controlgrid in such a phase as to obtain undamping of the input-circuit and/or a decrease in the inputcapacity of the tube.

2. A circuit for the amplification of high frequencies comprising an electmn discharge tube provided with at least a cathode, a control grid,

an anode, and a pair of secondary electron emitting electrodes interposed in the space between the control grid and anode, an output impedance connected between the anode and one o! the secondary electron emitting electrodes, an input impedance connected between the control grid and cathode, and a composite impedance having one portion connected between the other of said secondary electron emitting electrodes and the control grid and another portion between said other emitting electrode and the cathode, the portions of said composite impedance being of such value and the current supplied to the control grid through said composite impedance being of such phase that the effective input impedance of the circuit and the input capacity of the tube are reduced.

3. A circuit for the amplification of high irequencies comprising an electron discharge tube provided with at least a cathode, a control grid,

an anode, and a pair of secondary electron emit- I ting electrodes interposed in the space between the control grid and anode, an output resonant circuit connected between the anode and one 01 v and a second impedance connected between said other emitting electrode and the cathode, said impedances being chosen 01 such sign and value as to reduce the damping oi the input circuit and/or'to decrease the input capacity oi the tube.

" 4. A circuit for the amplification of high frequenciescomprising an electron discharge tube provided with at least a cathode, a control grid, an anode, and a pair or secondary electron emitting electrodes interposed in the space between the control grid and anode, an output circuit connected between the anode and one of the secondary electron emitting electrodes, a tunableinput circuit connected between the control grid and cathode, a capacitive reactance connected between the other of said secondary electron,

an anode, and a pair of secondary electron-emitting electrodes interposed in the space between the control grid and anode, anoutput circuit having its electrical center connected. to the cathode connected between the anode'and one of the secondary electron emitting electrodes, an

input circuit connected between the control grid and cathode, a first impedance connected between the other of said secondary electron emitting electrodes and the control grid, and a second impedance between said electrode and the cathode, said impedances being chosen of such sign and value that the input-capacity of the tube is substantially reduced.

6. A circuit in accordance with the invention defined in claim 5, wherein the first and second impedancesare each constituted by a resistance.

"l. A circuit in accordance with the invention defined in claim 5, wherein the first impedance is constituted by a capacity and the second impedanceis constituted by a resistance.

Mam-MAN JULIUS o'r'ro STRUTT. ALDERT vim mm ZlEL. I 

